The subject matter disclosed herein relates to direct drive motors for use in a non-invasive, non-destructive imaging system. By way of example, the present discussion relates the use of certain segmented direct drive motors in the context of a computed tomography imaging system.
Non-invasive imaging technologies allow images of the internal structures or features of a patient to be obtained without performing an invasive procedure on the patient. In particular, such non-invasive imaging technologies rely on various physical principles, such as the differential transmission of X-rays through the target volume or the reflection of acoustic waves, to acquire data and to construct images or otherwise represent the observed internal features of the patient.
For example, in computed tomography (CT) and other X-ray based imaging technologies, X-ray radiation spans a subject of interest, such as a human patient, and a portion of the radiation impacts a detector where the image data is collected. In digital X-ray systems a photo detector produces signals representative of the amount or intensity of radiation impacting discrete pixel regions of a detector surface. The signals may then be processed to generate an image that may be displayed for review. In CT systems a detector array, including a series of detector elements, produces similar signals through various positions as a gantry is displaced around a patient.
In particular, in CT imaging systems the gantry is conventionally used to spin the X-ray source and detector components around the imaging volume in which the patient is positioned during a scan. Some CT systems may employ a direct drive motors to spin the CT gantry, to which the X-ray tube and the detector are affixed, around the patient. As used herein, a direct drive motor, in contrast to a belt drive or geared drive, applies power from a motor to a driven load (here a CT gantry) without any reductions in power, such as may be associated with a gearbox. In conventional direct drive contexts, the direct drive motor assembly is typically provided as a full 360 degree ring structure.
Such a construction provides a variety of challenges to fabrication and use. For example, traditionally CT scanners have needed high torque motors to accelerate and decelerate the gantry quickly in order to minimize the amount of time that the components on the rotating gantry spend under the high gravitational (i.e., high-G) forces. Such high torque motors have conventionally required a large number of windings, which equates to greater complexity, greater weight, and greater expense of the motor. Similarly, the expense and complexity of these motors has limited the availability of direct drive motor technology, which is generally quieter, to higher end systems.
In addition, direct drive designs utilizing a full ring structure also present certain challenges in terms of maintenance and servicing. In particular, while direct drive motors can provide benefits to a CT such as quiet and smooth operation, they cannot be replaced in the hospital like a belt driven CT gantry can (which utilize a smaller motor plus a belt driven system). Direct drive motor armatures are typically too large and heavy to replace in a hospital room.